Canadian journal of microbiology最新文献

Understanding the microbial diversity is the first step to monitor the microbial quality of agricultural surface waters. Here we report a study comparing the microbial composition and diversities in agricultural surface waters in Ontario, Canada, including the streams adjacent to dairy cattle production in eastern Ontario and the field runoffs from the manure-impacted experimental farm of south-western Ontario. We also studied the quality of the surface water in the western basin of Lake Erie during a harmful algal bloom (cHAB). In eastern Ontario, we found significantly lower (P < 0.01) abundance of Proteobacteria and Burkholderiales in the streams adjacent to dairy production than the non-agriculture site. Bacteroidetes was more abundant (P < 0.0001) in medium/high order streams and agriculture/urban mixed site. Seasonal peaks of Flavobacterium were observed in low order streams but the trend was not in medium/high order streams. In south-western Ontario, the dominant bacterial taxa in field runoffs was Pseudomonas, regardless of manure types. We also discovered that the elevated total dissolved nitrogen, total dissolved phosphorus and chlorophyll a associated with the cHAB zone in Lake Erie was further away rather from the agricultural sites. In conclusion, our studies identified unique microbiome patterns associated with agricultural surface waters in Ontario.

Fusarium head blight (FHB) is a devastating fungal disease caused by Fusarium graminearum, which affects barley (Hordeum vulgare L.) and other small cereal grains. Fungal endophytes are microorganisms that reside inside tissues and considered that they may have been involved in various roles of the plants. This study involved the comparison of fungal endophytes between "non-infected/clean" and "FHB-infected" barley genotypes in various tissues collected at different plant developmental stages and were grown under different conditions (i.e., greenhouse, research field, and FHB-field nursery). We hypothesized that fungal endophytes diversity and abundance may differ between plant tissues in various barley genotypes that were non-infected and FHB-infected. The 18S-internal transcribed spacer sequencing analysis revealed a greater number of fungal operational taxonomic units (OTUs) and endophyte species in FHB-infected barley compared to clean barley. A one-way ANOVA and Tukey's pairwise comparison test (p ≤ 0.05) were performed to test significant differences. Higher seed endophyte diversity was found in FHB-infected (120 OTUs) compared to non-infected (113 OTUs) harvested in 2021. The increase in diversity of endophytes that contributes to different roles in plant protection and defense, such as biocontrol agents, may prevent the growth of Fusarium species and decrease FHB-infection.

The genus Flavobacterium constitutes a vast pool of microorganisms living in multiple environmental niches including fish pathogens and species in the fish microbiome. Veterinary reports have identified flavobacteria in fish from Quebec's fish farms, confirming their association with infections. However, these reports have not conducted in-depth characterization, and the diversity of nonpathogenic flavobacteria in Quebec remains unknown. This study is the first step in assessing the diversity of Flavobacterium in Quebec's fish farms, without focusing solely on pathogenic strains. Seventeen isolates were collected from different fish farms, from either the water or fish. Microbial species identification was performed using PCR genotyping of the gyrB gene, whole-genome sequencing, and phylogenetic analysis. Antimicrobial susceptibility tests for tetracycline and florfenicol, the two most commonly used antibiotics in Quebec aquaculture, along with predictive tools, were employed to assess resistance. This study revealed potential new species among the isolates. No known pathogenic species were detected, and all 17 isolates clustered within CIIIb or CIIIc, recently described phylogenetic clades of Flavobacterium found in various environments, and the majority showed resistance to antibiotics. This study highlights the expanding diversity of Flavobacterium, particularly among species associated with fish, and underscores the need for further research in Quebec.

Antimicrobial resistance has a negative impact on people's health and the economy. New resistance mechanisms are emerging, making the treatment of infections very challenging. Fungi are well known for their production of secondary metabolites during active cell growth. In this study, a strain of Penicillium sanguifluum (111-12) was isolated from Manitoba soil and investigated for antimicrobial properties of fungal secondary metabolites against pathogenic bacteria, and two fungal plant pathogens that are known for causing Dutch elm diseases and chestnut blight disease. Penicillium sanguifluum (111-12) produced dehydrocurvularin (C1) and 11-hydroxycurvularin (C2). C1 and C2 were examined for their antimicrobial properties and these compounds were combined with various antibiotics to evaluate their potentiation (adjuvant) properties. Promising results were obtained for C1 that decreased the minimum inhibitory concentrations of cefepime, ceftazidime, tobramycin, and amikacin against a clinical multidrug resistant strain of Pseudomonas aeruginosa (PA82). In addition, C1 and C2 showed no impact on the Galleria mellonella model regarding toxicity.

Highlights: Cannabidiol (CBD) decreases the growth of C. albicans. CBD inhibits the yeast-to-hyphae transition. CBD reduces biofilm formation by C. albicans. CBD induces C. albicans death through necrosis.

Acinetobacter baumannii is an opportunistic pathogen that is often studied in commonly used rich media in laboratories worldwide. Due to the metabolic versatility of A. baumannii, it can be cultured in different growth mediums; however, this can lead to genotypic and phenotypic variations. In this study, we compared phenotypic and transcriptomic changes in A. baumannii ATCC17978-VU cultured in M9 minimal media supplemented with 20 mmol/L sodium succinate and rich lysogeny broth media. Phenotypically, growth was significantly slowed, virulence in Galleria mellonella was attenuated, and susceptibility to a variety of antibiotic classes was reduced when A. baumannii ATCC17978-VU was grown in minimal media versus rich media. Transcriptomic analysis showed differential regulation of >700 genes-including those associated with energy production and ribosomal function-when the two growth conditions were compared, with the majority of the upregulated genes seen in minimal media of unknown function. This study showed that culture media has a profound effect on the phenotype and cellular workings of a bacteria, highlighting the need for more studies of pathogens like A. baumannii ATCC17978-VU in minimal media.

Climate change is rapidly altering Arctic marine environments, leading to warmer waters, increased river discharge, and accelerated sea ice melt. The Hudson Bay Marine System experiences the fastest rate of sea ice loss in the Canadian North resulting in a prolonged open water season during the summer months. We examined microbial communities in the Hudson Strait using high throughput 16s rRNA gene sequencing during the peak of summer, in which the bay was almost completely ice-free, and air temperatures were high. We found that salinity and temperature significantly affected the taxonomic composition among microbial communities across sites. We observed a higher relative abundance of specific Polaribacter sp. Amplicon sequence variants (ASVs) at more saline sites. Shannon diversity was not significantly impacted by salinity or temperature. These results contribute to our understanding of surface water microbial community composition in the Hudson Strait and shed light on how future salinity and temperature conditions may favour certain microbial populations.

Salmonella enterica is a major foodborne pathogen capable of surviving in low-water-activity (a_W) foods and retaining the ability to invade intestinal epithelial cells after environmental stress, such as exposure to high salt concentrations. Although multiple serotypes tolerate low a_W, Tennessee strains have been repeatedly linked to outbreaks in dry foods, suggesting specific adaptations. This study evaluated the effects of NaCl (1%, 4%, and 6%) on growth, biofilm formation, post-biofilm recovery, and internalization capacity (Caco-2 cell assays) of six S. enterica strains-four Tennessee and two serogroup B isolates-from peanuts, raisins, chocolate, and dehydrated tomatoes. Growth and biofilm formation were monitored over a 7-day exposure to NaCl; post-biofilm recovery and internalization were assessed afterward. While all strains showed reduced internalization after salt exposure, Tennessee isolates generally maintained higher growth and biofilm formation than the ATCC 14028 reference strain. Phenotypic responses varied by strain and NaCl concentration, indicating differences in osmotic stress adaptation. The persistence of internalization capacity, even at reduced levels, highlights a potential food safety risk in NaCl-preserved products. These findings emphasize the need to consider strain-specific traits when developing control measures for Salmonella in dry food environments.

The pathogenic Pseudomonas aeruginosa utilizes a quorum-sensing pathway for biofilm formation. The quorum-sensing proteins LasI and LasR of the Las system, alongside the swarming motility protein BswR, play a crucial role in the biofilm-mediated antibiotic resistance phenomenon. In this in silico study, LasI, LasR, and BswR were the prime targets for binding studies by promising drug candidates like linalool, ferutinin, citronellal, and carvacrol. These monoterpenoid compounds are carefully considered for this study due to their reported anti-microbial activity. Among all, carvacrol exhibited the highest binding energies with LasI (-5.932 kcal/mol), LasR (-7.469 kcal/mol), and BswR (-4.42 kcal/mol). Furthermore, the MMGBSA scores between carvacrol and LasI, LasR, and BswR individually are -33.14, -54.22, and -41.86 kcal/mol, which further corroborated the strong binding. During 100 ns of simulation, the ligand binds to the active sites of these proteins through the H-bonds at Ile107 of LasI, Tyr47 of LasR, and Leu57 of BswR. In addition, the root-mean-square deviation values of the ligand-protein complex are within the appropriate range of less than 5 Å. Absorption, Distribution, Metabolism, Excretion, and Toxicity analysis confirmed that carvacrol has the most negligible toxicity to mammalian cells. Hence, this finding is the first report to show that carvacrol can inhibit the Pseudomonas aeruginosa biofilms.